ASP.NET MVC difference between input tag and anchor tag

Question

I'm curious why is input does not work? and the intellisense of vs to asp tag helper is not working I've just typed them.

 

if IntelliSense is not working does it means the thing I'm typing will not work?

 

<input type="button" value="Register" class="btn btn-sm btn-primary" asp-controller="Acccount" asp-action="Register"/>

 

<a class="btn btn-sm btn-primary" asp-controller="Account" asp-action="Register">Register</a>